Increasing size of lock icon on big screen devices

Lock icon can be very small on big devices because by default its padding is specified in pixels (48px) and its size is calculated in LockIconViewController to be 64dp.
When density is small enough that doesn't leave enough space for normal size of lock icon.
Now padding is overriden for sw600 to be density independent.

Fixes: 208440478
Test: manual on two different large screen devices on master and sc-v2
Change-Id: I73e1e06c23d782951b9cc45fb7bee349a2405593